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So here is a conundrum about star death and re-berth I could never wrap my head around. A star collapses and blows up to produce a supernova. That produces a nebula, which condenses and produces new stars and solar systems.

So here is a conundrum about star death and re-berth I could never wrap my head around. A star collapses and blows up to produce a supernova. That produces a nebula, which condenses and produces new stars and solar systems.

Wait, conservation of mass?

What's the conundrum? Massive stars (8+ solar masses) explode at the end of their lives when their cores produce iron (Type Ib, Ic, and II), which is unable to fuse into heavier elements. The stars undergoes sudden gravitational collapse (with speeds up to 70,000 kph/43,495 mph or 23% the speed of light), with the core compressing to a critical density (i.e. neutron star). The process releases enough energy to blast the remaining outer layers of lighter elements into interstellar space. The resultant shock wave can trigger the formation of new stars. In fact, depending on the initial mass of the star, a good chuck of the stars mass has already been ejected before the remaining star explodes.

I believe that roughly half of the mass is converted into energy, with 99% of it carried away in a 10 second burst of neutrinos (1058). An early warning system called SNEWS consists of a network of neutrino detectors that is programmed to send an alert if two detectors see a burst within 10 seconds of each other. This allows astronomers to train their instruments on that patch of the sky.

That leaves plenty of mass thrown out to begin the next generation of stars. I believe subsequent generations are smaller.

It's estimated that supernova occur at a rate of 10 per second in the universe.

So here is a conundrum about star death and re-berth I could never wrap my head around. A star collapses and blows up to produce a supernova. That produces a nebula, which condenses and produces new stars and solar systems.

Wait, conservation of mass?

What's the conundrum? Massive stars (8+ solar masses) explode at the end of their lives when their cores produce iron (Type Ib, Ic, and II), which is unable to fuse into heavier elements. The stars undergoes sudden gravitational collapse (with speeds up to 70,000 kph/43,495 mph or 23% the speed of light), with the core compressing to a critical density (i.e. neutron star). The process releases enough energy to blast the remaining outer layers of lighter elements into interstellar space. The resultant shock wave can trigger the formation of new stars. In fact, depending on the initial mass of the star, a good chuck of the stars mass has already been ejected before the remaining star explodes.

I believe that roughly half of the mass is converted into energy, with 99% of it carried away in a 10 second burst of neutrinos (1058). An early warning system called SNEWS consists of a network of neutrino detectors that is programmed to send an alert if two detectors see a burst within 10 seconds of each other. This allows astronomers to train their instruments on that patch of the sky.

That leaves plenty of mass thrown out to begin the next generation of stars. I believe subsequent generations are smaller.

It's estimated that supernova occur at a rate of 10 per second in the universe.

I think I understand now. So it has to be a massive star that explodes to eject enough stuff to create new stars. Still, I have to digest all of this information. Thanks Arg. Are you a physicist?

Yeah, the earliest stars were enormous beasts. The bigger the star, the hotter it is, the faster it burns through its fuel, and the quicker it dies. All the elements heavier than iron are made in the supernova of these dying stars, which ultimately produced the materials necessary for rocky planets, and life. Our sun is believed to be a second or third generation star, containing hydrogen and helium created during the Big Bang, along with heavier elements created when the first generation stars exploded.

No, not a physicist, but I've taken numerous courses. At one point I was dreaming of becoming an astronomer, but sitting on a mountaintop all night had its downsides. Lol. I currently live on a steady diet of space-related documentaries, e.g. How the Universe Works. They peak my curiosity enough to do some additional research on the topics. I have way more questions than answers on topics such as dark matter, black holes, interstellar space, star formation, etc. The universe is truly wonderful.

Yeah, the earliest stars were enormous beasts. The bigger the star, the hotter it is, the faster it burns through its fuel, and the quicker it dies. All the elements heavier than iron are made in the supernova of these dying stars, which ultimately produced the materials necessary for rocky planets, and life. Our sun is believed to be a second or third generation star, containing hydrogen and helium created during the Big Bang, along with heavier elements created when the first generation stars exploded.

No, not a physicist, but I've taken numerous courses. At one point I was dreaming of becoming an astronomer, but sitting on a mountaintop all night had its downsides. Lol. I currently live on a steady diet of space-related documentaries, e.g. How the Universe Works. They peak my curiosity enough to do some additional research on the topics. I have way more questions than answers on topics such as dark matter, black holes, interstellar space, star formation, etc. The universe is truly wonderful.

You just touched on another question I had bouncing around in my head, about our sun being a 2nd or 3rd generation star. I always wondered where the heavy elements came from when our sun was formed from clouds of H. But then, if there was all this heavy stuff floating around, why didn't our sun just form a super huge planet with a rocky core?

You just touched on another question I had bouncing around in my head, about our sun being a 2nd or 3rd generation star. I always wondered where the heavy elements came from when our sun was formed from clouds of H. But then, if there was all this heavy stuff floating around, why didn't our sun just form a super huge planet with a rocky core?

The sun does contain heavy elements, but they represent only a tiny fraction of the overall mass of the sun. It's 70% hydrogen and 28% helium. Carbon, nitrogen, and oxygen make up 1.5%, and the other 0.5% are small amounts of the heavier elements, e.g. iron, silicon, magnesium.

While a supernova does create the heavier elements, they remain a small fraction of the amount of hydrogen and helium in the universe. Keep in mind that the sun is 333,000 times the mass of the Earth. 1.3 million Earths could fit inside the sun. If the sun swallowed our planet, it would add 0.0003% more heavy elements.

So basically, the sun has over 1000 Earth's worth of heavy elements in its core. I'm not exactly sure how a star initially forms, but I wouldn't be surprised if a large rocky clump sits in the middle of the protoplanetary disc, pulling in the hydrogen and helium until sufficient mass has built up to ignite the star.

You just touched on another question I had bouncing around in my head, about our sun being a 2nd or 3rd generation star. I always wondered where the heavy elements came from when our sun was formed from clouds of H. But then, if there was all this heavy stuff floating around, why didn't our sun just form a super huge planet with a rocky core?

The sun does contain heavy elements, but they represent only a tiny fraction of the overall mass of the sun. It's 70% hydrogen and 28% helium. Carbon, nitrogen, and oxygen make up 1.5%, and the other 0.5% are small amounts of the heavier elements, e.g. iron, silicon, magnesium.

While a supernova does create the heavier elements, they remain a small fraction of the amount of hydrogen and helium in the universe. Keep in mind that the sun is 333,000 times the mass of the Earth. 1.3 million Earths could fit inside the sun. If the sun swallowed our planet, it would add 0.0003% more heavy elements.

So basically, the sun has over 1000 Earth's worth of heavy elements in its core. I'm not exactly sure how a star initially forms, but I wouldn't be surprised if a large rocky clump sits in the middle of the protoplanetary disc, pulling in the hydrogen and helium until sufficient mass has built up to ignite the star.

I guess my question is if our galaxy condensed from a huge nebula, why is the sun 70% H, while the inner planets are mostly Fe, Ni, and Si? There seems to have been a selective condensation happening. The inner 4 planets are rocky iron based, while the sun and the rest of them are gas based. It's almost like galactic chromatography but with separation based on gravity rather than BP?

I guess my question is if our galaxy condensed from a huge nebula, why is the sun 70% H, while the inner planets are mostly Fe, Ni, and Si? There seems to have been a selective condensation happening. The inner 4 planets are rocky iron based, while the sun and the rest of them are gas based. It's almost like galactic chromatography but with separation based on gravity rather than BP?

When the sun ignited, the blast of solar wind blew away the lighter elements in the inner solar system, leaving primarily the heavy elements. That's why we have small, rocky planets near the sun.

I guess my question is if our galaxy condensed from a huge nebula, why is the sun 70% H, while the inner planets are mostly Fe, Ni, and Si? There seems to have been a selective condensation happening. The inner 4 planets are rocky iron based, while the sun and the rest of them are gas based. It's almost like galactic chromatography but with separation based on gravity rather than BP?

When the sun ignited, the blast of solar wind blew away the lighter elements in the inner solar system, leaving primarily the heavy elements. That's why we have small, rocky planets near the sun.

I remember hearing that on a number of documentaries, just forgot.Then a perturbation in the orbits of Jupiter and Saturn brought water bearing comets raining in upon the newborn earth from the oort cloud. It's awesome how the formation of our little goldilocks section of the galaxy was so fortuitous. Although it is calculated that there are billions x billions possible planets in similar proximate orbits as our earth across the universe, how many could have undergone such fortuitous events as ours? I guess the answer is still billions...

There is also a theory that either Neptune, or the yet-to-be-found Planet 9 tugged Jupiter to its current location, as it was much closer to the Sun, In the process it cleared out our little corner of the solar system. Otherwise we would have very likely crashed into Jupiter eons ago.

In the Universe, the saying goes, "If you're one in a billion, there are a billion of them just like you".

The ESA's Gaia spacecraft team has released the most detailed map of the Milky Way ever created. The map contains ~1.7 billion stars. Every pinpoint of light on the image is a star or distant galaxy. What's more amazing is that the data represents less than 1% of the total stars in our galaxy (250 billion +/- 150 billion).

The ESA's Gaia spacecraft team has released the most detailed map of the Milky Way ever created. The map contains ~1.7 billion stars. Every pinpoint of light on the image is a star or distant galaxy. What's more amazing is that the data represents less than 1% of the total stars in our galaxy (250 billion +/- 150 billion).

Those are the Large and Small Magellanic Clouds. They are dwarf galaxies that orbit just outside the Milky Way ~160,000 to 200,000 light years away. By comparison the Andromeda galaxy is 2.5 million light-years away. The two galaxies orbit the Milky Way once every 1.5 billion years. The LMC contains ~30 billion stars, and the SMC contains ~3 billion stars. The LMC is 14,000 light-years across, and the SMC is 7000 light-years across.

Those are the Large and Small Magellanic Clouds. They are dwarf galaxies that orbit just outside the Milky Way ~160,000 to 200,000 light years away. By comparison the Andromeda galaxy is 2.5 million light-years away. The two galaxies orbit the Milky Way once every 1.5 billion years. The LMC contains ~30 billion stars, and the SMC contains ~3 billion stars. The LMC is 14,000 light-years across, and the SMC is 7000 light-years across.

Those lines are their respective paths? Cool. But, if those magellanic clouds are orbiting the milky way, that means they are engaged in our gravity (and us in theirs)? That is mind blowing. Space is indeed awesome.

Yes, the LMC and SMC are gravitationally bound to our galaxy, and are know as satellite galaxies. There are roughly 15 other dwarf satellite galaxies. The Milky Way will eventually swallow them up before long, just as it has with many other dwarf galaxies that used to orbit nearby.

Over the next few billion years all galaxies in the Local Group will merge into one large galaxy, likely an elliptical galaxy.

A edge on view of Saturn and its rings taken by Cassini on 3 March 2006. The moons Mimas and (tiny) Janus are above, and Tethys is below. As the Maitre D said in Monty Python's Meaning of Life, "It's only wafer thin."

First image from the Transiting Exoplanet Survey Satellite (TESS), as it heads out towards its final elliptical orbit around the earth. Once in position TESS will survey ~200,000 stars within 300 light-years from Earth. This image captures only 0.25% of the amount of sky that TESS will image.

The central portion of star cluster RCW 38. Located 5,500 light-years from Earth, the area is littered with young, hot, massive stars that will live fast and die young. Many will very likely explode as supernovae. The image was taken with the HAWK-I infrared imager, allowing it to peer through the dusty cluster. The radiation emitted from the young stars causes the surrounding gas to glow blue.